BEags:
"Stateful firewall" means that there is a built-in firewall on the Voyager which keeps track of all the connections your laptop makes to other computers. If it receives a packet from the outside world which it can't reconcile with a request from your lappy, it will stop it. It can be configured to be as strict or lax as you want.
Microfilters need to be on any ordinary phone plugged into an extension. If there's nothing plugged in, you don't need one.